The present invention relates to a hydraulic actuator employing a limit adjustable mechanical lock. More particularly, the present invention relates to a hydraulic actuator employing a limit adjustable mechanical lock, capable of preventing an error in the operation of a valve by removing the fine operating clearance of a valve and by stopping the operation of the valve under hydraulic pressure equal to or less than preset pressure.
In general, various valves have been employed to cut off and control the flow of a fluid. The valves are automatically or manually open or closed.
Although some of the valves have structures that may be manually manipulated, the valves are open or closed through automatic manipulation in significantly various fields.
As operating units of the valves are automatically open or closed, electrical actuators based on solenoids and hydraulic actuators based a fluid, such as air or oil, have been extensively employed.
However, the electrical actuators have been applied to small valves that do not require great operating force while the hydraulic actuators have been applied to medium and large valves.
Among them, in the case of the hydraulic actuators, significantly various operating structures have been suggested and used. In the case of the hydraulic actuators, there have been suggested a configuration in which a piston formed integrally with a rack gear is moved by a predetermined distance through hydraulic pressure to rotate a pinion gear engaged with the rack gear of the piston and a valve shaft shaft-fixed to the pinion gear, thereby rotating a valve coupled to a valve shaft such that the valve is open or closed.
However, according to the related art, in the case of the hydraulic actuator, the piston simply operating by the hydraulic pressure is rotated and the valve is open or closed by the rotational force of the piston. Even if hydraulic pressure is applied to the piston in insufficient amount, the piston may move so that errors occur in the operation of the valve.
In addition, even if a fluid passage is initially closed or open to the maximum extent by the valve, if the rack gear of the piston is engaged with the pinion gear to rotate the valve, the difference may be slightly made between the moment that the rack gear of the piston is engaged with the pinion gear and the moment that the valve is open or closed, and a fluid may leak by the difference.